Near field communication devices, systems, and methods using q factor adjustments

ABSTRACT

An NFC (near field communication) device can include a resonance unit and an NFC chip. The resonance unit may communicate with an external device through an electromagnetic wave. The NFC chip can provide output data to the resonance unit, receive input data from the resonance unit, and can reduce a Q factor (quality factor) of the resonance unit when a signal receive operation is performed in a card mode, and can maintain the Q factor of the resonance unit in a reader mode and when a signal transmit operation is performed in the card mode.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 USC §119 to Korean PatentApplication No. 10-2013-0024614, filed on Mar. 7, 2013, in the KoreanIntellectual Property Office (KIPO), the contents of which are hereinincorporated by reference in their entirety.

FIELD

The invention relates to wireless communication technology, and moreparticularly to near field communication (NFC) devices.

BACKGROUND

NFC devices are extensively employed in mobile devices. As the mobiledevice is miniaturized, an antenna included in the NFC device may alsobe miniaturized. If the antenna included in the NFC device isminiaturized, the bandwidth may be reduced so that errors may occurduring high-speed data communication.

SUMMARY

According to example embodiments, an NFC (near field communication)device includes a resonance unit and an NFC chip. The resonance unitmakes data communication with an external device through anelectromagnetic wave. The NFC chip provides output data to the resonanceunit, receives input data from the resonance unit, reduces a Q factor(quality factor) of the resonance unit when a signal receive operationis performed in a card mode, and maintains the Q factor of the resonanceunit in a reader mode and when a signal transmit operation is performedin the card mode.

In example embodiments, the NFC chip may connect a terminal connected tothe resonance unit to a ground voltage through a pull-down load when thesignal receive operation is performed in the card mode and cut off theterminal connected to the resonance unit from the ground voltage in thereader mode and when the signal transmit operation is performed in thecard mode.

In example embodiments, the NFC chip may measure a voltage supplied fromthe resonance unit and control a reduction degree of the Q factor of theresonance unit based on a magnitude of the measured voltage when thesignal receive operation is performed in the card mode.

According to example embodiments, an NFC (near field communication)device includes a resonance unit, a rectifier, a regulator and a Q(quality) sink unit. The resonance unit generates a first voltage inresponse to an electromagnetic wave. The rectifier generates a secondvoltage by rectifying the first voltage. The regulator generates aninternal voltage having a voltage level of a constant magnitude by usingthe second voltage to output the internal voltage to a first node. The Q(quality) sink unit may be connected between the first node and a groundvoltage, turn on to reduce a Q factor (quality factor) of the resonanceunit when a signal receive operation is performed in a card mode, andturn off to maintain the Q factor in a reader mode and when a signaltransmit operation is performed in the card mode.

In example embodiments, the Q sink unit may include a Q sink controllerconfigured to generate a Q sink signal enabled when the signal receiveoperation is performed in the card mode and disabled in the reader modeand when the signal transmit operation is performed in the card mode,and a pull-down unit configured to connect the first node to the groundvoltage through a pull-down load when the Q sink signal is enabled andto cut off the first node from the ground voltage when the Q sink signalis disabled.

The NFC device may further include a central processing unit (CPU)configured to generate a mode signal that represents the card mode orthe reader mode and the signal receive operation or the signal transmitoperation when the mode is the card mode, wherein the Q sink controllergenerates the Q sink signal based on the mode signal.

The pull-down unit may include a switch connected to the first node andturned on in response to the Q sink signal, and a current sourceconnected between the switch and the ground voltage to generate acurrent having a constant magnitude.

The pull-down unit may include a slew control unit configured togenerate first to n^(th) Q sink sub-signals, which are sequentiallyenabled at a first time interval, when the Q sink signal is enabled andto generate first to n^(th) Q sink sub-signals, which are sequentiallydisabled at the first time interval, when the Q sink signal is disabled,first to n¹ switches connected to the first node and turned on inresponse to the first to n^(th) Q sink sub-signals, respectively, andfirst to n^(th) current sources connected between the first to n^(th)switches and the ground voltage, respectively, to generate a currenthaving a constant magnitude.

The pull-down unit may include a switch connected to the first node andturned on in response to the Q sink signal, and a resistor connectedbetween the switch and the ground voltage.

The pull-down unit may include a slew control unit configured togenerate first to n^(th) Q sink sub-signals, which are sequentiallyenabled at a first time interval, when the Q sink signal is enabled andto generate first to n^(th) Q sink sub-signals, which are sequentiallydisabled at the first time interval, when the Q sink signal is disabled,first to n^(th) switches connected to the first node and turned on inresponse to the first to n^(th) Q sink sub-signals, respectively, andfirst to n^(th) resistors connected between the first to n^(th) switchesand the ground voltage, respectively.

In example embodiments, the NFC device may further include a fielddetector configured to receive the first voltage to generate a fieldintensity signal corresponding to a magnitude of the first voltage,wherein the Q sink unit controls a reduction degree of the Q factor ofthe resonance unit based on the field intensity signal when the signalreceive operation is performed in the card mode.

The Q sink unit may include a Q sink controller configured to generate aQ sink signal enabled when the signal receive operation is performed inthe card mode and disabled in the reader mode and when the signaltransmit operation is performed in the card mode and to generate a Qfactor tuning signal based on the field intensity signal, and apull-down unit configured to connect the first node to the groundvoltage through a pull-down load having a magnitude corresponding to theQ factor tuning signal when the Q sink signal is enabled and to cut offthe first node from the ground voltage when the Q sink signal isdisabled.

The pull-down unit may include a switch connected to the first node andturned on in response to the Q sink signal, and a variable currentsource connected between the switch and the ground voltage to generate acurrent having a magnitude corresponding to the Q factor tuning signal.

The pull-down unit may include a slew control unit configured togenerate first to n^(th) Q sink sub-signals, which are sequentiallyenabled at a first time interval, when the Q sink signal is enabled andto generate first to n^(th) Q sink sub-signals, which are sequentiallydisabled at the first time interval, when the Q sink signal is disabled,first to n^(th) switches connected to the first node and turned on inresponse to the first to n^(th) Q sink sub-signals, respectively, andfirst to n^(th) variable current sources connected between the first ton^(th) switches and the ground voltage, respectively, to generate acurrent having a magnitude corresponding to the Q factor tuning signal.

The pull-down unit may include a switch connected to the first node andturned on in response to the Q sink signal, and a variable resistorconnected between the switch and the ground voltage and having aresistance with a magnitude corresponding to the Q factor tuning signal.

The pull-down unit may include a slew control unit configured togenerate first to n^(th) Q sink sub-signals, which are sequentiallyenabled at a first time interval, when the Q sink signal is enabled andto generate first to n^(th) Q sink sub-signals, which are sequentiallydisabled at the first time interval, when the Q sink signal is disabled,first to n^(th) switches connected to the first node and turned on inresponse to the first to n^(th) Q sink sub-signals, respectively, andfirst to n^(th) variable resistors connected between the first to n^(th)switches and the ground voltage, respectively, and having a resistancewith a magnitude corresponding to the Q factor tuning signal.

According to example embodiments, an NFC (near field communication)device includes a resonance unit and a transmit unit. The resonance unitgenerates an electromagnetic wave corresponding to a transmit signalreceived from a transmit terminal in a reader mode. The transmit unitgenerates the transmit signal corresponding to output data to providethe transmit data to the transmit terminal in the reader mode, reduces aQ factor (quality factor) of the resonance unit when a signal receiveoperation is performed in a card mode, and maintains the Q factor when asignal transmit operation is performed in the card mode.

In example embodiments, the transmit unit may connect the transmitterminal to a supply voltage through a pull-up load or connect thetransmit terminal to a ground voltage through a pull-down load based onthe output data in the reader mode, connect the transmit terminal to theground voltage through the pull-down load when the signal receiveoperation is performed in the card mode, and cut off the transmitterminal from the ground voltage and the supply voltage when the signaltransmit operation is performed in the card mode.

In example embodiments, the transmit unit may include a pull-uptransistor connected between the supply voltage and the transmitterminal, a pull-down transistor connected between the ground voltageand the transmit terminal, and a driving unit configured to selectivelyturn on one of the pull-up transistor and the pull-down transistor basedon the output data in the reader mode, to turn off the pull-uptransistor while turning on the pull-down transistor when the signalreceive operation is performed in the card mode, and to turn off thepull-up transistor and the pull-down transistor when the signal transmitoperation is performed in the card mode.

The NFC device may further include a central processing unit (CPU)configured to generate a mode signal that represents the card mode orthe reader mode and the signal receive operation or the signal transmitoperation when the mode is the card mode, wherein the driving unitdrives the pull-yup transistor and the pull-down transistor based on themode signal.

In example embodiments, the transmit unit may include first to n^(th)pull-up transistors connected in parallel between the supply voltage andthe transmit terminal, first to n^(th) pull-down transistors connectedin parallel between the ground voltage and the transmit terminal, and adriving unit configured to turn on the first to n^(th) pull-uptransistors or the first to n^(th) pull-down transistors based on theoutput data in the reader mode, to turn off the first to n^(th) pull-uptransistors while sequentially turning on the first to n^(th) pull-downtransistors at a first time interval when the signal receive operationis performed in the card mode, and to turn off the first to n^(th)pull-up transistors while sequentially turning off the first to n^(th)pull-down transistors at the first time interval when the signaltransmit operation is performed in the card mode.

In example embodiments, the NFC device may further include a fielddetector configured to measure a voltage supplied from the resonanceunit to generate a field intensity signal corresponding to a magnitudeof the measured voltage in the card mode, wherein the transmit unitcontrols a reduction degree of the Q factor of the resonance unit basedon the field intensity signal when the signal receive operation isperformed in the card mode.

The transmit unit may include first to n^(th) pull-up transistorsconnected in parallel between the supply voltage and the transmitterminal, first to n^(th) pull-down transistors connected in parallelbetween the ground voltage and the transmit terminal, and a driving unitconfigured to turn on the first to n^(th) pull-up transistors or thefirst to n^(th) pull-down transistors based on the output data in thereader mode, to select k pull-down transistors (k is a positive integerequal to or less than n) among the first to n^(th) pull-down transistorsbased on the field intensity signal in the card mode, to turn off thefirst to n^(th) pull-up transistors and (n−k) pull-down transistors,which are not selected, while sequentially turning on the k pull-downtransistors at a first time interval when the signal receive operationis performed in the card mode, and to turn off the first to n^(th)pull-up transistors and (n−k) pull-down transistors, which are notselected, while sequentially turning off the k pull-down transistors atthe first time interval when the signal transmit operation is performedin the card mode.

According to example embodiments, an electronic system includes an NFC(near field communication) device, a memory device and an applicationprocessor. The NFC device makes communication with an external devicethrough an NFC. The memory device stores output data and input data. Theapplication processor controls operations of the NFC device and thememory device. The NFC device includes a resonance unit configured totransmit the output data to the external device through anelectromagnetic wave, and an NFC chip configured to provide the outputdata to the resonance unit, to receive the input data from the resonanceunit, to reduce a Q factor (quality factor) of the resonance unit when asignal receive operation is performed in a card mode, and to maintainthe Q factor of the resonance unit in a reader mode and when a signaltransmit operation is performed in the card mode.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative, non-limiting example embodiments will be more clearlyunderstood from the following detailed description taken in conjunctionwith the accompanying drawings.

FIG. 1 is a block diagram illustrating an NFC (near field communication)device according to an example embodiment.

FIG. 2 is a graph to explain the operation of the NFC device of FIG. 1.

FIG. 3 is a block diagram illustrating an example of the NFC device ofFIG. 1.

FIG. 4 is a block diagram illustrating an example of a Q sink unitincluded in the NFC device of FIG. 3.

FIG. 5 is a diagram illustrating an example of a pull-down unit includedin the Q sink unit of FIG. 4.

FIG. 6 is a diagram illustrating an example of a pull-down unit includedin the Q sink unit of FIG. 4.

FIG. 7 is a block diagram illustrating an example of a pull-down unitincluded in the Q sink unit of FIG. 4.

FIG. 8 is a block diagram illustrating an example of a pull-down unitincluded in the Q sink unit of FIG. 4.

FIG. 9 is a view to explain the operation of a slew control unitincluded in the pull-down unit of FIGS. 7 and 8.

FIG. 10 is a block diagram illustrating an example of the NFC device ofFIG. 1.

FIG. 11 is a block diagram illustrating an example of a Q sink unitincluded in the NFC device of FIG. 10.

FIG. 12 is a diagram illustrating an example of a pull-down unitincluded in the Q sink unit of FIG. 11.

FIG. 13 is a diagram illustrating an example of a pull-down unitincluded in the Q sink unit of FIG. 11.

FIG. 14 is a block diagram illustrating an example of a pull-down unitincluded in the Q sink unit of FIG. 11.

FIG. 15 is a block diagram illustrating an example of a pull-down unitincluded in the Q sink unit of FIG. 11.

FIG. 16 is a view to explain the operation of the NFC devices of FIGS. 3and 10.

FIGS. 17A and 17B are views to explain the effects of the NFC devices ofFIGS. 3 and 10.

FIG. 18 is a block diagram illustrating an example of the NFC device ofFIG. 1.

FIG. 19 is a block diagram illustrating an example of a transmit unitincluded in the NFC device of FIG. 18.

FIG. 20 is a block diagram illustrating an example of a transmit unitincluded in the NFC device of FIG. 18.

FIG. 21 is a view to explain the operation of a driving unit included inthe transmit unit of FIG. 20.

FIG. 22 is a block diagram illustrating an example of the NFC device ofFIG. 1.

FIG. 23 is a block diagram illustrating an example of a transmit unitincluded in the NFC device of FIG. 22.

FIG. 24 is a view to explain the operation of a driving unit included inthe transmit unit of FIG. 23.

FIG. 25 is a block diagram illustrating an electronic system accordingto example embodiments.

DETAILED DESCRIPTION OF THE EMBODIMENTS ACCORDING TO THE INVENTIVECONCEPT

Various example embodiments will be described more fully with referenceto the accompanying drawings, in which some example embodiments areshown. The present inventive concept may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the present inventive concept to those skilled inthe art. Like reference numerals refer to like elements throughout thisapplication.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are used to distinguish oneelement from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of the present inventiveconcept. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. Other words used to describe therelationship between elements should be interpreted in a like fashion(e.g., “between” versus “directly between,” “adjacent” versus “directlyadjacent,” etc.).

The terminology used herein is for the purpose of describing particularembodiments and is not intended to be limiting of the inventive concept.As used herein, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes” and/or “including,” when used herein, specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this inventive concept belongs. Itwill be further understood that terms, such as those defined in commonlyused dictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

FIG. 1 is a block diagram illustrating an NFC (near field communication)device according to an example embodiment.

The NFC device 10 illustrated in FIG. 1 makes communication with anexternal device through an NFC scheme. The NFC device 10 makes datacommunication with an external reader based on an electromagnetic wave(EMW) supplied from the external reader in a card mode, where the NFCdevice 10 serves as a card and makes data communication with an externalcard based on the EMW generated from the NFC device 10 in a reader modewhere the NFC device 10 serves as a reader.

Referring to FIG. 1, the NFC device 10 includes a resonance unit 100 andan NFC chip 200.

Upon the signal receive operation, the resonance unit 100 receives inputdata from the external device through the EMW and the NFC chip 200receives the input data from the resonance unit 100. Upon the signaltransmit operation, the NFC chip 200 provides output data to theresonance unit 100 and the resonance unit 100 transmits the output datato the external device through the EMW.

The resonance unit 100 may include a resonance circuit including anantenna having an inductance component and a resonance capacitor.

In the card mode, the resonance unit 100 provides a signal, which isinduced in response to the EMW received from the external device, to theNFC chip 200 and the NFC chip 200 performs the signal receive operationby generating the input data by demodulating the signal. In the cardmode for a signal transmit operation, the NFC chip 200 provides amodulation signal, which is generated by modulating the output data, tothe resonance unit 100 and the resonance unit 100 may perform the signaltransmit operation by reflecting the EMW received from the externaldevice based on the modulation signal.

In the reader mode, the NFC chip 200 can provide a transmit signal aspart of a signal transmit operation, which is obtained by synthesizingthe modulation signal generated by modulating the output data with acarrier signal, to the resonance unit 100 and the resonance unit 100provides the transmit signal in the form of the EMW to the externaldevice to perform the signal transmit operation. In the reader mode, theNFC chip 200 can provide a signal as part of a signal receive operation,which is induced in response to the EMW reflected from the externaldevice, and the NFC chip 200 generates the input data by demodulatingthe signal to perform the signal receive operation.

The NFC chip 200 reduces the Q factor (quality factor) of the resonanceunit 100 when the signal receive operation is performed in the card modeand maintains the Q factor in the reader mode and when the signaltransmit operation is performed in the card mode.

For instance, the NFC chip 200 may reduce the Q factor of the resonanceunit 100 when the signal receive operation is performed in the card modeby connecting a terminal connected to the resonance unit 100 to a groundvoltage GND through a pull-down load. In addition, the NFC chip 200 maymaintain the Q factor in the reader mode and when the signal transmitoperation is performed in the card mode by cutting off the terminalconnected to the resonance unit 100 from the ground voltage GND.

FIG. 2 is a graph to explain the operation of the NFC device of FIG. 1.

In FIG. 2, a first graph A represents the frequency characteristic ofthe resonance unit 100.

Referring to FIG. 2, the resonance unit 100 may have the longitudinalfrequency characteristic having the center on the carrier frequency fc.The resonance unit 100 may have the maximum gain MAX1 at the carrierfrequency fc and may have a first bandwidth BW1 where a first frequencyf1 and a second frequency f2 serve as cutoff frequencies. The Q factorof the resonance unit 100 may have a value obtained by dividing thecarrier frequency fc by the first bandwidth BW1.

Since the NFC chip 200 maintains the Q factor of the resonance unit 100in the reader mode and when the signal transmit operation is performedin the card mode, the resonance unit 100 may have the frequencycharacteristic as shown in the first graph A in the reader mode and whenthe signal transmit operation is performed in the card mode.

As appreciated by the present inventors, if the frequency characteristicof the resonance unit 100 is not changed when the signal receiveoperation is performed in the card mode, as shown in FIG. 2, ahigh-speed signal having the high frequency fu equal to or higher thanthe second frequency f2 (for instance, the high frequency of 848 Kbps ormore) is filtered by the resonance unit 100, so the NFC chip 200 may notnormally demodulate the input data provided from the external device.Thus, the NFC device 100 may not perform the high-speed communication.

The bandwidth BW1 of the resonance unit 100 is reduced as the size ofthe antenna included in the resonance unit 100 becomes reduced and theintensity of the EMW received from the external device becomes weak, sothe available communication speed of the NFC device 10 may be furtherlimited.

However, as described above, the NFC chip 200 included in the NFC device10 can reduce the Q factor of the resonance unit 100 when the signalreceive operation is performed in the card mode. For instance, the NFCchip 200 reduces the gain of the resonance unit 100 by connecting theterminal connected to the resonance unit 100 to the ground voltage GNDthrough the pull-down load when the signal receive operation isperformed in the card mode, so the resonance unit 100 may have thefrequency characteristic as shown in a second graph B of FIG. 2. At thistime, the resonance unit 100 may have the maximum gain MAX2 at thecarrier frequency fc and may have a second bandwidth BW2 where a thirdfrequency f3 and a fourth frequency f4 serve as cutoff frequencies.Since the Q factor of the resonance unit 100 may have a value obtainedby dividing the carrier frequency fc by the second bandwidth BW2, the Qfactor of the resonance unit 100 is reduced.

In this case, as shown in FIG. 2, even when the resonance unit 100receives the high-speed signal having the high frequency fu equal to orhigher than the second frequency f2 (for instance, the high frequency of848 Kbps or more), the high-speed signal can be normally receivedwithout being filtered. Thus, the available communication speed of theNFC device 10 may be increased.

Meanwhile, since the load modulation characteristic is lowered as thegain of the resonance unit 100 is reduced in the signal transmitoperation, as described above, the NFC chip 200 cuts off the terminalconnected to the resonance unit 100 from the ground voltage GND when thesignal transmit operation is performed, so that the Q factor of theresonance unit 100 can be maintained.

In one example embodiment, the NFC chip 200 may measure a voltagesupplied from the resonance unit 100 through the terminal connected tothe resonance unit 100 when the signal receive operation is performed inthe card mode in order to control the reduction degree of the Q factorof the resonance unit 100 based on the magnitude of the measuredvoltage. For instance, if the voltage supplied from the resonance unit100 has a relatively great magnitude (that is, when operated in a nearfield), the Q factor of the resonance unit 100 is relatively small. Inaddition, if the voltage supplied from the resonance unit 100 has arelatively small magnitude (that is, when operated in a far field), theQ factor of the resonance unit 100 is relatively great. Therefore, theNFC chip 200 may increase the reduction degree of the Q factor of theresonance unit 100 as the voltage supplied from the resonance unit 100is small when the signal receive operation is performed in the cardmode.

FIG. 3 is a block diagram illustrating an example of the NFC device ofFIG. 1.

Only elements to operate the NFC device 10 a in the card mode areillustrated in FIG. 3 and elements to operate the NFC device 10 a in thereader mode are omitted in FIG. 3

Referring to FIG. 3, the NFC device 10 a may include a resonance unit100 and an NFC chip 200 a.

The NFC chip 200 a may be connected to the resonance unit 100 through afirst power terminal L1 and a second power terminal L2.

The resonance unit 100 may include a resonance circuit having an antennaL and a first capacitor C1 and a filter having a second capacitor C2 toprovide an induction voltage induced in response to the EMW to the firstpower terminal L1 and the second power terminal L2 and a third capacitorC3. The resonance unit 100 may supply the induction voltage induced inresponse to the EMW to the NFC chip 200 a as a first voltage V1 throughthe filter.

The configuration of the resonance unit 100 illustrated in FIG. 3 is anexample only and the configuration of the resonance unit 100 accordingto example embodiments may not be limited to the above, but may bevariously modified.

The NFC chip 200 a may receive the first voltage V1 from the resonanceunit 100 through the first power terminal L1 and the second powerterminal L2.

The NFC chip 200 a may include a rectifier 210, a regulator 220, a Qsink unit 230, a central processing unit (CPU) 240, a power switch PSW,a memory 250, a demodulator 251 and a modulator 253.

The rectifier 210 can generate a second voltage V2 by rectifying thefirst voltage V1.

The regulator 220 can generate an internal voltage Vint having a voltagelevel of a predetermined magnitude usable in the NFC chip 200 a by usingthe second voltage V2 and can provide the internal voltage Vint to afirst node N1.

The CPU 240 can control the overall operation of the NFC chip 200 a. TheCPU 240 may operate by receiving a supply voltage VDD from a powersource, such as a battery. In addition, the CPU 240 may receive theinternal voltage Vint through the power switch PSW. When the supplyvoltage VDD has a predetermined level or more, the CPU 240 may operateby using the supply voltage VDD and disable a power control signal PCSto turn off the power switch PSW. Meanwhile, when the supply voltage VDDhas a level less than the predetermined level, the CPU 240 enables thepower control signal PCS to turn on the power switch PSW such that theCPU 240 can be operated by using the internal voltage Vint supplied fromthe regulator 220.

When the signal receive operation is performed in the card mode, thedemodulator 251 generates the input data by demodulating the signalsupplied from the resonance unit 100 through the first and second powerterminals L1 and L2 to provide the input data to the CPU 240. The CPU240 may store the input data in the memory 250.

When the signal transmit operation is performed in the card mode, theCPU 240 reads out the output data from the memory 250 to provide theoutput data to the modulator 253 and the modulator 253 may modulate theoutput data to provide a modulation signal to the first and second powerterminals L1 and L2. For instance, the modulator 253 can generate themodulation signal by performing load modulation with respect to theoutput data.

The Q sink unit 230 may be connected between the first node N1 and theground voltage GND. The Q sink unit 230 is turned on when the signalreceive operation is performed in the card mode to reduce the Q factorof the resonance unit 100 and turned off in the reader mode and when thesignal transmit operation is performed in the card mode to maintain theQ factor of the resonance unit 100.

In one example embodiment, the CPU 240 provides a mode signal MD, whichrepresents the card mode or the reader mode and the signal receiveoperation or the signal transmit operation, to the Q sink unit 230,whereupon the Q sink unit 230 may selectively reduce the Q factor of theresonance unit 100 based on the mode signal MD.

FIG. 4 is a block diagram illustrating an example of the Q sink unitincluded in the NFC device of FIG. 3.

Referring to FIG. 4, the Q sink unit 230 may include a pull-down unit231 and a Q sink controller 233.

The Q sink controller 233 may generate a Q sink signal QSS which isenabled when the signal receive operation is performed in the card modeand is disabled in the reader mode and when the signal transmitoperation is performed in the card mode. For instance, the Q sinkcontroller 233 may generate the Q sink signal QSS based on the modesignal MD received from the CPU 240.

The pull-down unit 231 may connect the first node N1 to the groundvoltage GND through the pull-down load when the Q sink signal QSS isenabled and cut off the first node N1 from the ground voltage GND whenthe Q sink signal QSS is disabled.

FIG. 5 is a diagram illustrating an example of the pull-down unitincluded in the Q sink unit of FIG. 4.

Referring to FIG. 5, the pull-down unit 231 a may include a switch SWand a current source Io.

The switch SW may be connected between the first node N1 and the currentsource Io and the current source Io may be connected between the switchSW and the ground voltage GND. Otherwise, the current source Io may beconnected between the first node N1 and the switch SW and the switch SWmay be connected between the current source Io and the ground voltageGND.

The switch SW may be turned on when the Q sink signal QSS is enabled andturned off when the Q sink signal QSS is disabled.

The current source Io may generate a current having a constantmagnitude.

As illustrated in FIG. 5, the pull-down unit 231 a may selectivelyreduce the Q factor of the resonance unit 100 by connecting a currentload between the first node N1 and the ground voltage GND based on the Qsink signal QSS.

FIG. 6 is a diagram illustrating another example of the pull-down unitincluded in the Q sink unit of FIG. 4.

Referring to FIG. 6, the pull-down unit 231 b may include a switch SWand a resistor Ro.

The switch SW may be connected between the first node N1 and theresistor Ro and the resistor Ro may be connected between the switch SWand the ground voltage GND. Otherwise, the resistor Ro may be connectedbetween the first node N1 and the switch SW and the switch SW may beconnected between the resistor Ro and the ground voltage GND.

The switch SW may be turned on when the Q sink signal QSS is enabled andturned off when the Q sink signal QSS is disabled.

The resistor Ro may have a constant resistance value.

As illustrated in FIG. 6, the pull-down unit 231 b may selectivelyreduce the Q factor of the resonance unit 100 by connecting a resistiveload between the first node N1 and the ground voltage GND based on the Qsink signal QSS.

FIG. 7 is a block diagram illustrating an example of the pull-down unitincluded in the Q sink unit of FIG. 4.

Referring to FIG. 7, the pull-down unit 231 c may include a slew controlunit 232, first to n^(th) switches SW1, SW2, . . . , and SWn and firstto n^(th) current sources Io-1, Io-2, . . . , and Io-n, wherein N is aninteger of 2 or more.

FIG. 9 is a view to explain the operation of the slew control unitincluded in the pull-down unit of FIG. 7.

Referring to FIG. 9, the slew control unit 232 may generate first ton^(th) Q sink sub-signals QSS1, QSS2, . . . , and QSSn, which aresequentially enabled at a first time interval Td, when the Q sink signalQSS is enabled and may generate first to n^(th) Q sink sub-signals QSS1, QSS2, . . . , and QSSn, which are sequentially disabled at the firsttime interval Td, when the Q sink signal QSS is disabled.

Referring again to FIG. 7, the first to n^(th) switches SW1, SW2, . . ., and SWn are connected in parallel to the first node N1, the first ton^(th) current sources Io-1, Io-2, . . . , and Io-n are connected inparallel to the ground voltage GND, and the first to n^(th) switchesSW1, SW2, . . . , and SWn as well as the first to n^(th) current sourcesIo-1, Io-2, . . . , and Io-n are connected with each other in series,respectively.

The first to n^(th) switches SW1, SW2, . . . , and SWn may be turned onwhen the first to n^(th) Q sink sub-signals QSS1, QSS2, . . . , and QSSnare enabled, respectively, and may be turned off when the first ton^(th) Q sink sub-signals QSS1, QSS2, and QSSn are disabled,respectively.

The first to n^(th) current sources Io-1, Io-2, . . . , and Io-n maygenerate the current having a constant magnitude.

As shown in FIG. 7, the pull-down unit 231 c may selectively reduce theQ factor of the resonance unit 100 by connecting a current load betweenthe first node N1 and the ground voltage GND based on the Q sink signalQSS.

As appreciated by the present inventors, when the pull-down unit 231 cconcurrently turns on or turns off the first to n^(th) switches SW1,SW2, . . . , and SWn, the magnitude of the first voltage V1 supplied tothe NFC chip 200 a from the resonance unit 100 may sway in a moment sothat the error may occur during the data communication unless otherwiseaddressed.

As described above, since the pull-down unit 231 c sequentially turns onthe first to n^(th) current sources Io-1, Io-2, . . . , and Io-n at thefirst time interval Td when the Q sink signal QSS is enabled andsequentially turns off the first to n^(th) current sources Io-1, Io-2, .. . , and Io-n at the first time interval Td when the Q sink signal QSSis disabled, the pull-down unit 231 c can reduce the sway of the firstvoltage V1 when changing the Q factor of the resonance unit 100.

FIG. 8 is a block diagram illustrating an example of the pull-down unitincluded in the Q sink unit of FIG. 4.

Referring to FIG. 8, the pull-down unit 231 d may include a slew controlunit 232, first to n^(th) switches SW1, SW2, and SWn and first to n^(th)resistors Ro-1, Ro-2, . . . , and Ro-n, wherein N is an integer of 2 ormore.

FIG. 9 is a view to explain the operation of the slew control unitincluded in the pull-down unit of FIG. 8.

Referring to FIG. 9, the slew control unit 232 may generate first ton^(th) Q sink sub-signals QSS1, QSS2, . . . , and QSSn, which aresequentially enabled at a first time interval Td, when the Q sink signalQSS is enabled and may generate first to n^(th) Q sink sub-signals QSS1,QSS2, . . . , and QSSn, which are sequentially disabled at the firsttime interval Td, when the Q sink signal QSS is disabled.

Referring again to FIG. 8, the first to n^(th) switches SW1, SW2, . . ., and SWn are connected in parallel to the first node N1, the first ton^(th) resistors Ro-1, Ro-2, . . . , and Ro-n are connected in parallelto the ground voltage GND, and the first to n^(th) switches SW1, SW2, .. . , and SWn as well as the first to n^(th) resistors Ro-1, Ro-2, . . ., and Ro-n are connected with each other in series, respectively.

The first to n^(th) switches SW1, SW2, . . . , and SWn may be turned onwhen the first to n^(th) Q sink sub-signals QSS1, QSS2, . . . , and QSSnare enabled, respectively, and may be turned off when the first ton^(th) Q sink sub-signals QSS1, QSS2, . . . , and QSSn are disabled,respectively.

The first to n^(th) resistors Ro-1, Ro-2, . . . , and Ro-n may have aconstant resistance value.

As shown in FIG. 8, the pull-down unit 231 d may selectively reduce theQ factor of the resonance unit 100 by connecting a resistive loadbetween the first node N1 and the ground voltage GND based on the Q sinksignal QSS.

As appreciated by the present inventors, when the pull-down unit 231 dconcurrently turns on or turns off the first to n^(th) switches SW1,SW2, . . . , and SWn, the magnitude of the first voltage V1 supplied tothe NFC chip 200 a from the resonance unit 100 may sway in a moment sothat the error may occur during the data communication unless otherwiseaddressed.

As described above, since the pull-down unit 231 d sequentially connectsthe first to n^(th) resistors Ro-1, Ro-2, . . . , and Ro-n between thefirst node N1 and the ground voltage GND at the first time interval Tdwhen the Q sink signal QSS is enabled and sequentially cuts off thefirst to n^(th) resistors Ro-1, Ro-2, . . . , and Ro-n connected betweenthe first node N1 and the ground voltage GND at the first time intervalTd when the Q sink signal QSS is disabled, the pull-down unit 231 d canprevent the sway of the first voltage V1 when changing the Q factor ofthe resonance unit 100.

FIG. 10 is a block diagram illustrating an example of the NFC device ofFIG. 1.

Only elements to operate the NFC device 10 b in the card mode areillustrated in FIG. 10 and elements to operate the NFC device 10 b inthe reader mode are omitted in FIG. 10

Referring to FIG. 10, the NFC device 10 b may include a resonance unit100 and an NFC chip 200 b.

The NFC device 10 b of FIG. 10 is similar to the NFC device 10 a of FIG.3 except that the NFC device 10 b of FIG. 10 further includes a fielddetector 260 and the Q sink unit 230 is replaced with a Q sink unit 235.Thus, in order to avoid redundancy, the following description will bemade while focusing on the field detector 260 and the Q sink unit 235without explaining the elements illustrated in the NFC device 10 a.

The field detector 260 may receive the first voltage V1 from theresonance unit 100 to measure the magnitude of the first voltage V1 andmay generate a field intensity signal FIS corresponding to the magnitudeof the first voltage V1. As the intensity of the EMW received from theexternal device becomes strong, the magnitude of the first voltage V1generated from the resonance unit 100 is increased, so the fieldintensity signal FIS may represent the intensity of EMW received fromthe external device.

The Q sink unit 235 may be connected between the first node N1 and theground voltage GND. Based on the mode signal MD supplied from the CPU240, the Q sink unit 235 is turned on to reduce the Q factor of theresonance unit 100 when the signal receive operation is performed in thecard mode and turned off to maintain the Q factor of the resonance unit100 in the reader mode and when the signal transmit operation isperformed in the card mode. In addition, the Q sink unit 235 may controlthe reduction degree of the Q factor of the resonance unit 100 based onthe field intensity signal FIS when the signal receive operation isperformed in the card mode.

FIG. 11 is a block diagram illustrating an example of the Q sink unitincluded in the NFC device of FIG. 10.

Referring to FIG. 11, the Q sink unit 235 may include a pull-down unit236 and a Q sink controller 238.

The Q sink controller 238 may generate a Q sink signal QSS which isenabled when the signal receive operation is performed in the card modeand is disabled in the reader mode and when the signal transmitoperation is performed in the card mode. For instance, the Q sinkcontroller 238 may generate the Q sink signal QSS based on the modesignal MD received from the CPU 240.

In addition, the Q sink controller 238 may generate a Q factor tuningsignal QTS[M−1:0] based on the field intensity signal FIS supplied fromthe field detector 260. The Q factor tuning signal QTS is an m-bitsignal and may have a value proportional to a magnitude of the fieldintensity signal FIS, wherein m is a positive integer.

The pull-down unit 236 may connect the first node N1 to the groundvoltage GND through the pull-down load having a magnitude correspondingto a magnitude of the Q factor tuning signal QTS when the Q sink signalQSS is enabled and cut off the first node N1 from the ground voltage GNDwhen the Q sink signal QSS is disabled.

FIG. 12 is a diagram illustrating an example of the pull-down unitincluded in the Q sink unit of FIG. 11.

Referring to FIG. 12, the pull-down unit 236 a may include a switch SWand a variable current source IV.

The switch SW may be connected between the first node N1 and thevariable current source IV and the variable current source IV may beconnected between the switch SW and the ground voltage GND. Otherwise,the variable current source IV may be connected between the first nodeN1 and the switch SW and the switch SW may be connected between thevariable current source IV and the ground voltage GND.

The switch SW may be turned on when the Q sink signal QSS is enabled andturned off when the Q sink signal QSS is disabled.

The variable current source IV may generate a current having a magnitudecorresponding to the magnitude of the Q factor tuning signal QTS.

As illustrated in FIG. 12, the pull-down unit 236 a may selectivelyreduce the Q factor of the resonance unit 100 by connecting a currentload between the first node N1 and the ground voltage GND based on the Qsink signal QSS.

In addition, when the pull-down unit 236 a reduces the Q factor of theresonance unit 100, the pull-down unit 236 a may adjust the reductiondegree of the Q factor of the resonance unit 100 by adjusting themagnitude of the current load connected between the first node N1 andthe ground voltage GND based on the Q factor tuning signal QTS.

FIG. 13 is a diagram illustrating an example of the pull-down unitincluded in the Q sink unit of FIG. 11.

Referring to FIG. 13, the pull-down unit 236 b may include a switch SWand a variable resistor RV.

The switch SW may be connected between the first node N1 and thevariable resistor RV and the variable resistor RV may be connectedbetween the switch SW and the ground voltage GND. Otherwise, thevariable resistor RV may be connected between the first node N1 and theswitch SW and the switch SW may be connected between the variableresistor RV and the ground voltage GND.

The switch SW may be turned on when the Q sink signal QSS is enabled andturned off when the Q sink signal QSS is disabled.

The variable resistor RV may have a resistance value corresponding tothe Q factor tuning signal QTS.

As illustrated in FIG. 13, the pull-down unit 236 b may selectivelyreduce the Q factor of the resonance unit 100 by connecting a resistiveload between the first node N1 and the ground voltage GND based on the Qsink signal QSS.

In addition, when the pull-down unit 236 b reduces the Q factor of theresonance unit 100, the pull-down unit 236 b may adjust the reductiondegree of the Q factor of the resonance unit 100 by adjusting themagnitude of the resistive load connected between the first node N1 andthe ground voltage GND based on the Q factor tuning signal QTS.

FIG. 14 is a block diagram illustrating an example of the pull-down unitincluded in the Q sink unit of FIG. 11.

Referring to FIG. 14, the pull-down unit 236 c may include a slewcontrol unit 237, first to n^(th) switches SW1, SW2, . . . , and SWn andfirst to n^(th) variable current sources IV-1, IV-2, . . . , and IV-n,wherein N is an integer of 2 or more.

As illustrated in FIG. 9, the slew control unit 237 may generate firstto n^(th) Q sink sub-signals QSS1, QSS2, . . . , and QSSn, which aresequentially enabled at a first time interval Td, when the Q sink signalQSS is enabled and may generate first to n^(th) Q sink sub-signals QSS1,QSS2, and QSSn, which are sequentially disabled at the first timeinterval Td, when the Q sink signal QSS is disabled.

The first to n^(th) switches SW1, SW2, . . . , and SWn are connected inparallel to the first node N1, the first to n^(th) variable currentsources IV-1, IV-2, . . . , and IV-n are connected in parallel to theground voltage GND, and the first to n^(th) switches SW1, SW2, . . . ,and SWn as well as the first to n^(th) variable current sources IV-1,IV-2, . . . , and IV-n are connected with each other in series,respectively.

The first to n^(th) switches SW1, SW2, . . . , and SWn may be turned onwhen the first to n^(th) Q sink sub-signals QSS1, QSS2, . . . , and QSSnare enabled, respectively, and may be turned off when the first ton^(th) Q sink sub-signals QSS1, QSS2, . . . , and QSSn are disabled,respectively.

The first to n^(th) variable current sources IV-1, IV-2, . . . , andIV-n may generate the current having a magnitude corresponding to themagnitude of the Q factor tuning signal QTS.

As shown in FIG. 14, the pull-down unit 236 c may selectively reduce theQ factor of the resonance unit 100 by connecting a current load betweenthe first node N1 and the ground voltage GND based on the Q sink signalQSS.

As appreciated by the present inventors, when the pull-down unit 236 cconcurrently turns on or turns off the first to n^(th) switches SW1,SW2, . . . , and SWn, the magnitude of the first voltage V1 supplied tothe NFC chip 200 b from the resonance unit 100 may sway in a moment sothat the error may occur during the data communication unless otherwiseaddressed.

As described above, since the pull-down unit 236 c sequentially turns onthe first to n^(th) variable current sources IV-1, IV-2, . . . , andIV-n at the first time interval Td when the Q sink signal QSS is enabledand sequentially turns off the first to n^(th) variable current sourcesIV-1, IV-2, . . . , and IV-n at the first time interval Td when the Qsink signal QSS is disabled, the pull-down unit 236 c can reduce thesway of the first voltage V1 when changing the Q factor of the resonanceunit 100.

In addition, when the pull-down unit 236 c reduces the Q factor of theresonance unit 100, the pull-down unit 236 c may adjust the reductiondegree of the Q factor of the resonance unit 100 by adjusting themagnitude of the current load connected between the first node N1 andthe ground voltage GND based on the Q factor tuning signal QTS.

FIG. 15 is a block diagram illustrating an example of the pull-down unitincluded in the Q sink unit of FIG. 11.

Referring to FIG. 15, the pull-down unit 236 d may include a slewcontrol unit 237, first to n^(th) switches SW1, SW2, . . . , and SWn andfirst to n^(th) variable resistors RV-1, RV-2, . . . , and RV-n, whereinN is an integer of 2 or more.

As illustrated in FIG. 9, the slew control unit 237 may generate firstto n^(th) Q sink sub-signals QSS1, QSS2, . . . , and QSSn, which aresequentially enabled at a first time interval Td, when the Q sink signalQSS is enabled and may generate first to n^(th) Q sink sub-signals QSS1,QSS2, . . . , and QSSn, which are sequentially disabled at the firsttime interval Td, when the Q sink signal QSS is disabled.

The first to n^(th) switches SW1, SW2, . . . , and SWn are connected inparallel to the first node N1, the first to n^(th) variable resistorsRV-1, RV-2, . . . , and RV-n are connected in parallel to the groundvoltage GND, and the first to n^(th) switches SW1, SW2, . . . , and SWnas well as the first to n^(th) variable resistors RV-1, RV-2, . . . ,and RV-n are connected with each other in series, respectively.

The first to n^(th) switches SW1, SW2, . . . , and SWn may be turned onwhen the first to n^(th) Q sink sub-signals QSS1, QSS2, . . . , and QSSnare enabled, respectively, and may be turned off when the first ton^(th) Q sink sub-signals QSS1, QSS2, . . . , and QSSn are disabled,respectively.

The first to n^(th) variable resistors RV-1, RV-2, . . . , and RV-n mayhave a resistance value corresponding to the Q factor tuning signal QTS.

As shown in FIG. 15, the pull-down unit 236 d may selectively reduce theQ factor of the resonance unit 100 by connecting a resistive loadbetween the first node N1 and the ground voltage GND based on the Q sinksignal QSS.

As appreciated by the present inventors, when the pull-down unit 236 dconcurrently turns on or turns off the first to n^(th) switches SW1,SW2, . . . , and SWn, the magnitude of the first voltage V1 supplied tothe NFC chip 200 b from the resonance unit 100 may sway in a moment sothat the error may occur during the data communication unless otherwiseaddressed.

As described above, since the pull-down unit 236 d sequentially connectsthe first to n^(th) variable resistors RV-1, RV-2, . . . , and RV-nbetween the first node N1 and the ground voltage GND at the first timeinterval Td when the Q sink signal QSS is enabled and sequentially cutsoff the first to n^(th) variable resistors RV-1, RV-2, . . . , and RV-nconnected between the first node N1 and the ground voltage GND at thefirst time interval Td when the Q sink signal QSS is disabled, thepull-down unit 236 d can reduce the sway of the first voltage V1 whenchanging the Q factor of the resonance unit 100.

In addition, when the pull-down unit 236 d reduces the Q factor of theresonance unit 100, the pull-down unit 236 d may adjust the reductiondegree of the Q factor of the resonance unit 100 by adjusting themagnitude of the resistive load connected between the first node N1 andthe ground voltage GND based on the Q factor tuning signal QTS.

FIG. 16 is a block diagram to explain the operation the NFC devices ofFIGS. 3 to 10.

As illustrated in FIG. 16, the Q sink controllers 233 and 238 maygenerate the Q sink signal QSS which is enabled when the signal receiveoperation RX is performed in the card mode and is disabled in the readermode and when the signal transmit operation TX is performed in the cardmode. Therefore, since the Q sink units 230 and 235 are turned on whenthe signal receive operation is performed in the card mode, theresonance unit 100 may have the frequency characteristic as shown in thesecond graph B of FIG. 2, so the Q factor of the resonance unit 100 maybe reduced. In addition, since the Q sink units 230 and 235 are turnedoff in the reader mode and when the signal transmit operation isperformed in the card mode, the resonance unit 100 may have thefrequency characteristic as shown in the first graph A of FIG. 2, so theQ factor of the resonance unit 100 may be maintained.

FIGS. 17A and 17B are views to explain the effects of the NFC devices ofFIGS. 3 and 10.

The graph shown in FIG. 17A represents the first voltage V1 supplied tothe NFC chips 200 a and 200 b from the resonance unit 100 in response tothe high-speed signal having a frequency of 848 Kbps when the resonanceunit 100 has the frequency characteristic as shown in the first graph Aof FIG. 2 because the Q factor of the resonance unit 100 is not reduced(i.e., maintained) when the signal receive operation is performed in thecard mode, and the graph shown in FIG. 17B represents the first voltageV1 supplied to the NFC chips 200 a and 200 b from the resonance unit 100in response to the high-speed signal having a frequency of 848 Kbps whenthe resonance unit 100 has the frequency characteristic as shown in thesecond graph B of FIG. 2 because the Q factor of the resonance unit 100is reduced when the signal receive operation is performed in the cardmode.

As shown in the graph of FIG. 17A, if the Q factor of the resonance unit100 is not reduced, the high-speed signal is filtered through theresonance unit 100 so that a signal corresponding to the first voltageV1 supplied to the NFC chips 200 a and 200 b from the resonance unit 100may be distorted. Thus, when the NFC chips 200 a and 200 b demodulatesthe signal corresponding to the first voltage V1 through the ASK(magnitude shift keying) scheme, the input data transmitted from theexternal device may not be normally received.

However, as shown in the graph of FIG. 17B, if the Q factor of theresonance unit 100 is reduced, the high-speed signal is not filteredthrough the resonance unit 100 so that a signal corresponding to thefirst voltage V1 supplied to the NFC chips 200 a and 200 b from theresonance unit 100 may not be distorted (or distorted less). Thus, whenthe NFC chips 200 a and 200 b demodulates the signal corresponding tothe first voltage V1 through the ASK (magnitude shift keying) scheme,the input data transmitted from the external device may be normallyreceived.

Therefore, the NFC devices 10 a and 10 b according to exampleembodiments can stably receive the high-speed signal when the signalreceive operation is performed without degrading the characteristic ofthe load modulation when the signal receive operation is performed.

FIG. 18 is a block diagram illustrating an example of the NFC device ofFIG. 1.

Elements used to operate the NFC device 10 c in the reader mode as wellas elements used to operate the NFC device 10 c in the card mode areillustrated in FIG. 18.

Referring to FIG. 18, the NFC device 10 c may include a resonance unit100 and an NFC chip 200 c.

The NFC chip 200 c may be connected to the resonance unit 100 through afirst power terminal L1, a second power terminal L2, a first transmitterminal TX1, a second transmit terminal TX2, and a receive terminal RX.

The resonance unit 100 may include a resonance circuit having an antennaL and a first capacitor C1, a first filter having a second capacitor C2and a third capacitor C3 to connect the resonance circuit to the firstand second power terminals L1 and L2, a second filter having a sixthcapacitor C6 to connect the resonance circuit to the receive terminalRX, and a matching unit including a fourth capacitor C4 and a fifthcapacitor C5 to connect the resonance circuit to the first transmitterminal TX1 and the second transmit terminal TX2 in order to performthe impedance matching.

The configuration of the resonance unit 100 illustrated in FIG. 18 is anexample only and the configuration of the resonance unit 100 accordingto example embodiments may not be limited to the above, but may bevariously modified.

The NFC chip 200 c may perform the signal transmit operation and thesignal receive operation through the first power terminal L1 and thesecond power terminal L2 in the card mode, perform the signal transmitoperation through the first transmit terminal TX1 and the secondtransmit terminal TX2 in the reader mode, and perform the signal receiveoperation through the receive terminal RX in the reader mode.

The NFC chip 200 c may include a rectifier 210, a regulator 220, acentral processing unit (CPU) 240, a power switch PSW, a memory 250, afirst demodulator 251, a first modulator 253, a second demodulator 271,a second modulator 273, an oscillator 275, a mixer 277 and a transmitunit 280.

The rectifier 210, the regulator 220, the power switch PSW, the firstdemodulator 251 and the first modulator 253 can be equivalent to theregulator 220, the power switch PSW, the demodulator 251 and themodulator 253 included in the NFC device 10 a of FIG. 3.

When the signal receive operation is performed in the reader mode, thesecond demodulator 271 generates the input data by demodulating thesignal supplied from the resonance unit 100 through the receive terminalRX to provide the input data to the CPU 240. The CPU 240 may store theinput data in the memory 250.

When the signal transmit operation is performed in the reader mode, theCPU 240 may read out the output data TD from the memory 250 to providethe output data TD to the second modulator 273, the second modulator 273may modulate the output data TD to generate a modulation signal, theoscillator 275 may generate a carrier signal having a frequencycorresponding to a carrier frequency (for instance, 13.56 MHz), and themixer 277 may generate a transmit modulation signal TMS by synthesizingthe carrier signal with the modulation signal.

The transmit unit 280 may be connected between the supply voltage VDDand the ground voltage GND.

The transmit unit 280 may receive the transmit modulation signal TMSfrom the mixer 277 to generate a transmit signal TS corresponding to thetransmit modulation signal TMS in the reader mode. The resonance unit100 may generate the EMW corresponding to the transmit signal TSsupplied from the transmit unit 280 through the first transmit terminalTX1 and the second transmit terminal TX2. For instance, in the readermode, the transmit unit 280 may connect the first transmit terminal TX1and the second transmit terminal TX2 to the supply voltage VDD through apull-up load or connect the first transmit terminal TX1 and the secondtransmit terminal TX2 to the ground voltage GND through a pull-down loadbased on the transmit modulation signal TMS so that the transmit signalTS may be generated from the first transmit terminal TX1 and the secondtransmit terminal TX2.

The transmit unit 280 may reduce the Q factor of the resonance unit 100when the signal receive operation is performed in the card mode and maymaintain the Q factor of the resonance unit 100 when the signal transmitoperation is performed in the card mode. For instance, the transmit unit280 may reduce the Q factor of the resonance unit 100 when the signalreceive operation is performed in the card mode by connecting the firsttransmit terminal TX1 and the second transmit terminal TX2 to the groundvoltage GND through the pull-down load and may maintain the Q factor ofthe resonance unit 100 when the signal transmit operation is performedin the card mode by cutting off the first transmit terminal TX1 and thesecond transmit terminal TX2 from the ground voltage GND and the supplyvoltage VDD.

In one example embodiment, the CPU 240 may provide the mode signal MD,which represents the card mode or the reader mode and the signal receiveoperation or the signal transmit operation when the mode is the cardmode, to the transmit unit 280 and the transmit unit 280 may selectivelyreduce the Q factor of the resonance unit 100 based on the mode signalMD.

FIG. 19 is a block diagram illustrating an example of the transmit unitincluded in the NFC device of FIG. 18.

Referring to FIG. 19, the transmit unit 280 a may include a firstpull-up transistor MP0, a second pull-up transistor MP1, a firstpull-down transistor MN0, a second pull-down transistor MN1 and adriving unit 281.

The first pull-up transistor MP0 and the second pull-up transistor MP1may be PMOS (p-type metal oxide semiconductor) transistors and the firstpull-down transistor MN0 and the second pull-down transistor MN1 may beNMOS (n-type metal oxide semiconductor) transistors.

The first pull-up transistor MP0 may be connected between the supplyvoltage VDD and the first transmit terminal TX1 and the first pull-downtransistor MN0 may be connected between the first transmit terminal TX1and the ground voltage GND.

The second pull-up transistor MP1 may be connected between the supplyvoltage VDD and the second transmit terminal TX2 and the secondpull-down transistor MN1 may be connected between the second transmitterminal TX2 and the ground voltage GND.

The driving unit 281 may drive the first pull-up transistor MP0 througha first pull-up driving signal UDS0, may drive the first pull-downtransistor MN0 through a first pull-down driving signal DDS0, may drivethe second pull-up transistor MP1 through a second pull-up drivingsignal UDS1, and may drive the second pull-down transistor MN1 through asecond pull-down driving signal DDS1.

The driving unit 281 may determine whether the NFC chip 200 c is in thecard mode or the reader mode and may determine the signal receiveoperation or the signal transmit operation when the mode is the cardmode based on the mode signal MD supplied from the CPU 240.

The driving unit 281 may selectively turn on one of the first pull-uptransistor MP0 and the first pull-down transistor MN0 and one of thesecond pull-up transistor MP1 and the second pull-down transistor MN1based on the transmit modulation signal TMS in the reader mode.

The driving unit 281 may turn off the first pull-up transistor MP0 andthe second pull-up transistor MP1 and may turn on the first pull-downtransistor MN0 and the second pull-down transistor MN1 when the signalreceive operation is performed in the card mode.

The driving unit 281 may turn off all of the first pull-up transistorMP0, the second pull-up transistor MP1, the first pull-down transistorMN0 and the second pull-down transistor MN1 when the signal transmitoperation is performed in the card mode.

As described above, the transmit unit 280 a drives the first pull-uptransistor MP0, the second pull-up transistor MP1, the first pull-downtransistor MN0 and the second pull-down transistor MN1 based on thetransmit modulation signal TMS in the reader mode to perform the normaloperation to provide the transmit modulation signal TMS to the resonanceunit 100. In addition, the transmit unit 280 a connects the firsttransmit terminal TX1 and the second transmit terminal TX2 to the groundvoltage GND through the first pull-down transistor MN0 and the secondpull-down transistor MN1, respectively, thereby reducing the Q factor ofthe resonance unit 100 when the signal receive operation is performed inthe card mode.

FIG. 20 is a block diagram illustrating another example of the transmitunit included in the NFC device of FIG. 18.

Referring to FIG. 20, the transmit unit 280 b may include (1-1)^(th) to(1-n)^(th) pull-up transistors MP0-1, MP0-2, . . . , and MP0-n, second-1to second-n pull-up transistors MP1-1, MP1-2, . . . , and MP1-n,(1-1)^(th) to (1-n)^(th) pull-down transistors MN0-1, MN0-2, . . . , andMN0-n, second-1 to second-n pull-down transistors MN1-1, MN1-2, . . . ,and MN1-n, and a driving unit 282.

The (1-1)^(th) to (1-n)^(th) pull-up transistors MP0-1, MP0-2, . . . ,and MP0-n and the second-1 to second-n pull-up transistors MP1-1, MP1-2,. . . , and MP1-n may be PMOS transistors, and the (1-1)^(th) to(1-n)^(th) pull-down transistors MN0-1, MN0-2, . . . , and MN0-n and thesecond-1 to second-n pull-down transistors MN1-1, MN1-2, . . . , andMN1-n may be the NMOS transistors.

The (1-1)^(th) to (1-n)^(th) pull-up transistors MP0-1, MP0-2, . . . ,and MP0-n may be connected in parallel between the supply voltage VDDand the first transmit terminal TX1, and the (1-1)^(th) to (1-n)^(th)pull-down transistors MN0-1, MN0-2, . . . , and MN0-n may be connectedin parallel between the first transmit terminal TX1 and the groundvoltage GND.

The second-n pull-up transistors MP1-1, MP1-2, . . . , and MP1-n may beconnected in parallel between the supply voltage VDD and the secondtransmit terminal TX2 and the second-1 to second-n pull-down transistorsMN1-1, MN1-2, . . . , and MN1-n may be connected in parallel between thesecond transmit terminal TX2 and the ground voltage GND.

The driving unit 282 may drive the (1-1)^(th) to (1-n)^(th) pull-uptransistors MP0-1, MP0-2, . . . , and MP0-n through (1-1)^(th) to(1-n)^(th) pull-up driving signals UDS0-1, UDS0-2, . . . , and UDS0-n,respectively, drive the (1-1)^(th) to (1-n)^(th) pull-down transistorsMN0-1, MN0-2, . . . , and MN0-n through (1-1)^(th) to (1-n)^(th)pull-down driving signals DDS0-1, DDS0-2, . . . , and DDS0-n,respectively, drive the second-n pull-up transistors MP1-1, MP1-2, . . ., and MP1-n through second-1 to second-n pull-up driving signals UDS1-1,UDS1-2, . . . , and UDS1-n, respectively, and drive the second-1 tosecond-n pull-down transistors MN1-1, MN1-2, . . . , and MN1-n throughsecond-1 to second-n pull-down driving signals DDS1-1, DDS1-2, . . . ,and DDS1-n, respectively.

The driving unit 282 may determine whether the NFC chip 200 c is in thecard mode or the reader mode and may determine the signal receiveoperation or the signal transmit operation when the mode is the cardmode based on the mode signal MD supplied from the CPU 240.

In the reader mode, the driving unit 282 may turn on the (1-1)^(th) to(1-n)^(th) pull-up transistors MP0-1, MP0-2, . . . , and MP0-n or the(1-1)^(th) to (1-n)^(th) pull-down transistors MN0-1, MN0-2, . . . , andMN0-n and may turn on the second-n pull-up transistors MP1-1, MP1-2, andMP1-n or the second-1 to second-n pull-down transistors MN1-1, MN1-2, .. . , and MN1-n based on the transmit modulation signal TMS.

In the card mode, the driving unit 282 generates the (1-1)^(th) to(1-n)^(th) pull-up driving signals UDS0-1, UDS0-2, . . . , and UDS0-nand the second-1 to second-n pull-up driving signals UDS1-1, UDS1-2, . .. , and UDS1-n having the logic high level, so the driving unit 282 canturn off the (1-1)^(th) to (1-n)^(th) pull-up transistors MP0-1, MP0-2,. . . , and MP0-n and the second-1 to second-n pull-up transistorsMP1-1, MP1-2, . . . , and MP1-n.

In addition, as shown in FIG. 21, the driving unit 282 may sequentiallyturn on the (1-1)^(th) to (1-n)^(th) pull-down transistors MN0-1, MN0-2,. . . , and MN0-n and the second-1 to second-n pull-down transistorsMN1-1, MN1-2, . . . , and MN1-n at the first time interval Td bysequentially enabling the (1-1)^(th) to (1-n)^(th) pull-down drivingsignals DDS0-1, DDS0-2, . . . , and DDS0-n and the second-1 to second-npull-down driving signals DDS1-1, DDS1-2, . . . , and DDS1-n at thefirst time interval Td when the signal receive operation RX is performedin the card mode.

Further, as shown in FIG. 21, the driving unit 282 may sequentially turnoff the (1-1)^(th) to (1-n)^(th) pull-down transistors MN0-1, MN0-2, . .. , and MN0-n and the second-1 to second-n pull-down transistors MN1-1,MN1-2, . . . , and MN1-n at the first time interval Td by sequentiallydisabling the (1-1)^(th) to (1-n)^(th) pull-down driving signals DDS0-1,DDS0-2, . . . , and DDS0-n and the second-1 to second-n pull-downdriving signals DDS1-1, DDS1-2, . . . , and DDS1-n at the first timeinterval Td when the signal transmit operation TX is performed in thecard mode.

As described above, the transmit unit 280 b drives the (1-1)^(th) to(1-n)^(th) pull-up transistors MP0-1, MP0-2, . . . , and MP0-n, thesecond-n pull-up transistors MP1-1, MP1-2, . . . , and MP1-n, the(1-1)^(th) to (1-n)^(th) pull-down transistors MN0-1, MN0-2, . . . , andMN0-n and the second-1 to second-n pull-down transistors MN1-1, MN1-2, .. . , and MN1-n based on the transmit modulation signal TMS in thereader mode to perform the normal operation to provide the transmitsignal TS to the resonance unit 100. In addition, when the signalreceive operation is performed in the card mode, the transmit unit 280 bconnects the first transmit terminal TX1 and the second transmitterminal TX2 to the ground voltage GND through the (1-1)^(th) to(1-n)^(th) pull-down transistors MN0-1, MN0-2, . . . , and MN0-n and thesecond-1 to second-n pull-down transistors MN1-1, MN1-2, . . . , andMN1-n, respectively, thereby reducing the Q factor of the resonance unit100.

As appreciated by the present inventors, when the transmit unit 280 bconcurrently turns on or off the (1-1)^(th) to (1-n)^(th) pull-downtransistors MN0-1, MN0-2, . . . , and MN0-n and the second-1 to second-npull-down transistors MN1-1, MN1-2, . . . , and MN1-n in the card mode,the magnitude of the voltage in the first power terminal L1 and thesecond power terminal L2 may sway in a moment so that the error mayoccur during the data communication unless otherwise addressed.

As described above, the transmit unit 280 b sequentially turns on the(1-1)^(th) to (1-n)^(th) pull-down transistors MN0-1, MN0-2, . . . , andMN0-n and the second-1 to second-n pull-down transistors MN1-1, MN1-2, .. . , and MN1-n at the first time interval Td when the signal receiveoperation is performed in the card mode, and sequentially turns off the(1-1)^(th) to (1-n)^(th) pull-down transistors MN0-1, MN0-2, . . . , andMN0-n and the second-1 to second-n pull-down transistors MN1-1, MN1-2, .. . , and MN1-n at the first time interval Td when the signal transmitoperation is performed in the card mode, thereby preventing the sway ofthe voltage in the first power terminal L1 and the second power terminalL2 when changing the Q factor of the resonance unit 100.

FIG. 22 is a block diagram illustrating an example of the NFC device ofFIG. 1.

Elements used to operate the NFC device 10 d in the reader mode as wellas elements used to operate the NFC device 10 d in the card mode areillustrated in FIG. 22.

Referring to FIG. 22, the NFC device 10 d may include a resonance unit100 and an NFC chip 200 d.

The NFC device 10 d of FIG. 22 is similar to the NFC device 10 c of FIG.18 except that the NFC device 10 d of FIG. 22 further includes a fielddetector 290 and the transmit unit 280 is replaced with a transmit unit285. Thus, in order to avoid redundancy, the following description willbe made while focusing on the field detector 290 and the transmit unit285 without explaining the elements illustrated in the NFC device 10 c.

The field detector 290 may measure the voltage supplied from theresonance unit 100 through the first power terminal L1 and the secondpower terminal L2 to generate a field intensity signal FIS correspondingto the magnitude of the measured voltage. As the intensity of the EMWreceived from the external device becomes strong, the magnitude of thevoltage supplied to the first power terminal L1 and the second powerterminal L2 from the resonance unit 100 is increased, so the fieldintensity signal FIS may represent the intensity of EMW received fromthe external device.

The transmit unit 285 may be connected between the supply voltage VDDand the ground voltage GND.

The transmit unit 285 may determine whether the NFC chip 200 d is in thecard mode or the reader mode and may determine the signal receiveoperation or the signal transmit operation when the mode is the cardmode based on the mode signal MD supplied from the CPU 240.

The transmit unit 285 may receive the transmit modulation signal TMSfrom the mixer 277 to generate the transmit signal TS corresponding tothe transmit modulation signal TMS in the reader mode. The resonanceunit 100 may generate the EMW corresponding to the transmit signal TSsupplied from the transmit unit 285 through the first transmit terminalTX1 and the second transmit terminal TX2. For instance, in the readermode, the transmit unit 285 may connect the first transmit terminal TX1and the second transmit terminal TX2 to the supply voltage VDD through apull-up load or connect the first transmit terminal TX1 and the secondtransmit terminal TX2 to the ground voltage GND through a pull-down loadbased on the transmit modulation signal TMS so that the transmit signalTS may be generated from the first transmit terminal TX1 and the secondtransmit terminal TX2.

The transmit unit 285 may reduce the Q factor of the resonance unit 100when the signal receive operation is performed in the card mode and maymaintain the Q factor of the resonance unit 100 when the signal transmitoperation is performed in the card mode. For instance, the transmit unit285 may reduce the Q factor of the resonance unit 100 when the signalreceive operation is performed in the card mode by connecting the firsttransmit terminal TX1 and the second transmit terminal TX2 to the groundvoltage GND through the pull-down load and may maintain the Q factor ofthe resonance unit 100 when the signal transmit operation is performedin the card mode by cutting off the first transmit terminal TX1 and thesecond transmit terminal TX2 from the ground voltage GND and the supplyvoltage VDD. In addition, the transmit unit 285 may control thereduction degree of the Q factor of the resonance unit 100 based on thefield intensity signal FIS when the signal receive operation isperformed in the card mode.

FIG. 23 is a block diagram illustrating an example of the transmit unitincluded in the NFC device of FIG. 22.

Referring to FIG. 23, the transmit unit 285 a may include (1-1)^(th) to(1-n)^(th) pull-up transistors MP0-1, MP0-2, . . . , and MP0-n, second-1to second-n pull-up transistors MP1-1, MP1-2, . . . , and MP1-n,(1-1)^(th) to (1-n)^(th) pull-down transistors MN0-1, MN0-2, . . . , andMN0-n, second-1 to second-n pull-down transistors MN1-1, MN1-2, . . . ,and MN1-n, and a driving unit 283.

The (1-1)^(th) to (1-n)^(th) pull-up transistors MP0-1, MP0-2, . . . ,and MP0-n and the second-1 to second-n pull-up transistors MP1-1, MP1-2,. . . , and MP1-n may be PMOS transistors, and the (1-1)^(th) to(1-n))^(th) pull-down transistors MN0-1, MN0-2, . . . , and MN0-n andthe second-1 to second-n pull-down transistors MN1-1, MN1-2, . . . , andMN1-n may be the NMOS transistors.

The (1-1)^(th) to (1-n)^(th) pull-up transistors MP0-1, MP0-2, . . . ,and MP0-n may be connected in parallel between the supply voltage VDDand the first transmit terminal TX1, and the (1-1)^(th) to (1-n)^(th)pull-down transistors MN0-1, MN0-2, . . . , and MN0-n may be connectedin parallel between the first transmit terminal TX1 and the groundvoltage GND.

The second-n pull-up transistors MP1-1, MP1-2, . . . , and MP1-n may beconnected in parallel between the supply voltage VDD and the secondtransmit terminal TX2 and the second-1 to second-n pull-down transistorsMN1-1, MN1-2, . . . , and MN1-n may be connected in parallel between thesecond transmit terminal TX2 and the ground voltage GND.

The driving unit 283 may drive the (1-1)^(th) to (1-n)^(th) pull-uptransistors MP0-1, MP0-2, . . . , and MP0-n through (1-1)^(th) to(1-n))^(th) pull-up driving signals UDS0-1, UDS0-2, . . . , and UDS0-n,respectively, drive the (1-1)^(th) to (1-n)^(th) pull-down transistorsMN0-1, MN0-2, . . . , and MN0-n through (1-1)^(th) to (1-n)^(th)pull-down driving signals DDS0-1, DDS0-2, . . . , and DDS0-n,respectively, drive the second-n pull-up transistors MP1-1, MP1-2, . . ., and MP1-n through second-1 to second-n pull-up driving signals UDS1-1,UDS1-2, . . . , and UDS1-n, respectively, and drive the second-1 tosecond-n pull-down transistors MN1-1, MN1-2, . . . , and MN1-n throughsecond-1 to second-n pull-down driving signals DDS1-1, DDS1-2, . . . ,and DDS1-n, respectively.

The driving unit 283 may determine whether the NFC chip 200 d is in thecard mode or the reader mode and may determine the signal receiveoperation or the signal transmit operation when the mode is the cardmode based on the mode signal MD supplied from the CPU 240.

In the reader mode, the driving unit 283 may turn on the (1-1)^(th) to(1-n)^(th) pull-up transistors MP0-1, MP0-2, . . . , and MP0-n or the(1-1)^(th) to (1-n))^(th) pull-down transistors MN0-1, MN0-2, . . . ,and MN0-n and may turn on the second-n pull-up transistors MP1-1, MP1-2,. . . , and MP1-n or the second-1 to second-n pull-down transistorsMN1-1, MN1-2, . . . , and MN1-n based on the transmit modulation signalTMS.

In the card mode, the driving unit 283 may select k pull-downtransistors from among the (1-1)^(th) to (1-n)^(th) pull-downtransistors MN0-1, MN0-2, . . . , and MN0-n and the second-1 to second-npull-down transistors MN1-1, MN1-2, . . . , and MN1-n based on the fieldintensity signal FIS. For instance, the driving unit 283 may select the(1-1)^(th) to (1-k)^(th) pull-down transistors MN0-1, MN0-2, . . . , andMN0-k and the second-1 to second-k pull-down transistors MN1-1, MN1-2, .. . , and MN1-k, wherein k is a positive integer equal to or less thann.

In the card mode, the driving unit 283 generates the (1-1)^(th) to(1-n)^(th) pull-up driving signals UDS0-1, UDS0-2, . . . , and UDS0-nand the second-1 to second-n pull-up driving signals UDS1-1, UDS1-2, . .. , and UDS1-n having the logic high level, so the driving unit 283 canturn off the (1-1)^(th) to (1-n)^(th) pull-up transistors MP0-1, MP0-2,. . . , and MP0-n and the second-1 to second-n pull-up transistorsMP1-1, MP1-2, . . . , and MP1-n. In addition, as shown in FIG. 24, thedriving unit 283 generates the (1-(k+1))^(th) to (1-n)^(th) pull-downdriving signals DDS0-(k+1), . . . , and DDS0-n and the second-(k+1) tosecond-n pull-down driving signals DDS1-(k+1), . . . , and DDS1-n havingthe logic low level, so the driving unit 283 can turn off the(1-(k+1))^(th) to (1-n)^(th) pull-down transistors MN0-(k+1), . . . ,and MN0-n and the second-(k+1) to second-n pull-down transistorsMN1-(k+1), . . . , and MN1-n, which are not selected.

In addition, as shown in FIG. 24, the driving unit 283 may sequentiallyturn on the (1-1)^(th) to (1-k)^(th) pull-down transistors MN0-1, MN0-2,. . . , and MN0-k and the second-1 to second-k pull-down transistorsMN1-1, MN1-2, . . . , and MN1-k at the first time interval Td bysequentially enabling the (1-1)^(th) to (1-k)^(th) pull-down drivingsignals DDS0-1, DDS0-2, . . . , and DDS0-k and the second-1 to second-kpull-down driving signals DDS1-1, DDS1-2, . . . , and DDS1-k at thefirst time interval Td when the signal receive operation RX is performedin the card mode.

Further, as shown in FIG. 24, the driving unit 283 may sequentially turnoff the (1-1)^(th) to (1-k)^(th) pull-down transistors MN0-1, MN0-2, . .. , and MN0-k and the second-1 to second-k pull-down transistors MN1-1,MN1-2, . . . , and MN1-k at the first time interval Td by sequentiallydisabling the (1-1)^(th) to (1-k)^(th) pull-down driving signals DDS0-1,DDS0-2, . . . , and DDS0-k and the second-1 to second-k pull-downdriving signals DDS1-1, DDS1-2, . . . , and DDS1-k at the first timeinterval Td when the signal transmit operation TX is performed in thecard mode.

As described above, the transmit unit 285 a drives the (1-1)^(th) to(1-n)^(th) pull-up transistors MP0-1, MP0-2, . . . , and MP0-n, thesecond-n pull-up transistors MP1-1, MP1-2, . . . , and MP1-n, the(1-1)^(th) to (1-n)^(th) pull-down transistors MN0-1, MN0-2, . . . , andMN0-n and the second-1 to second-n pull-down transistors MN1-1, MN1-2, .. . , and MN1-n based on the transmit modulation signal TMS in thereader mode to perform the normal operation to provide the transmitsignal TS to the resonance unit 100. In addition, when the signalreceive operation is performed in the card mode, the transmit unit 285 aconnects the first transmit terminal TX1 and the second transmitterminal TX2 to the ground voltage GND through the (1-1)^(th) to(1-k)^(th) pull-down transistors MN0-1, MN0-2, . . . , and MN0-k and thesecond-1 to second-k pull-down transistors MN1-1, MN1-2, . . . , andMN1-k, respectively, thereby reducing the Q factor of the resonance unit100. In addition, the transmit unit 285 a may control the reductiondegree of the Q factor of the resonance unit 100 by adjusting the number(k) of pull-down transistors to be turned on when the signal receiveoperation is performed in the card mode based on the field intensitysignal FIS.

As appreciated by the present inventors, when the transmit unit 285 aconcurrently turns on or off the (1-1)^(th) to (1-k)^(th) pull-downtransistors MN0-1, MN0-2, . . . , and MN0-k and the second-1 to second-kpull-down transistors MN1-1, MN1-2, . . . , and MN1-k in the card mode,the magnitude of the voltage in the first power terminal L1 and thesecond power terminal L2 may sway in a moment so that the error mayoccur during the data communication unless otherwise addressed.

As described above, the transmit unit 285 a sequentially turns on the(1-1)^(th) to (1-k)^(th) pull-down transistors MN0-1, MN0-2, . . . , andMN0-k and the second-1 to second-k pull-down transistors MN1-1, MN1-2, .. . , and MN1-k at the first time interval Td when the signal receiveoperation is performed in the card mode, and sequentially turns off the(1-1)^(th) to (1-k)^(th) pull-down transistors MN0-1, MN0-2, . . . , andMN0-k and the second-1 to second-k pull-down transistors MN1-1, MN1-2, .. . , and MN1-k at the first time interval Td when the signal transmitoperation is performed in the card mode, thereby preventing the sway ofthe voltage in the first power terminal L1 and the second power terminalL2 when changing the Q factor of the resonance unit 100.

FIG. 25 is a block diagram illustrating an electronic system accordingto example embodiments.

Referring to FIG. 25, an electronic system 1000 includes an applicationprocessor AP 1100, an NFC (near field communication) device 1200, amemory device 1300, a user interface 1400 and a power supply 1500. Insome embodiments, the electronic system 1000 may be a mobile phone, asmart phone, a personal digital assistant (PDA), a portable multimediaplayer (PMP), a digital camera, a music player, a portable game console,a navigation system, a laptop computer, etc.

The application processor 1100 may control overall operations of theelectronic system 1000. The application processor 1100 may executeapplications, such as a web browser, a game application, a video player,etc. In some embodiments, the application processor 1100 may include asingle core or multiple cores. For example, the application processor1100 may be a multi-core processor, such as a dual-core processor, aquad-core processor, a hexa-core processor, etc. The applicationprocessor 1100 may include an internal or external cache memory.

The memory device 1300 may store data used to operate the electronicsystem 1000. For example, the memory device 1300 may store a boot imagefor booting the electronic system 1000, data to be output to an externaldevice and input data received from the external device. For example,the memory device 1300 may be an electrically erasable programmableread-only memory (EEPROM), a flash memory, a phase change random accessmemory (PRAM), a resistance random access memory (RRAM), a nano floatinggate memory (NFGM), a polymer random access memory (PoRAM), a magneticrandom access memory (MRAM), a ferroelectric random access memory(FRAM), etc.

The NFC device 1200 may provide the data stored in the memory device1300 to the external device through NFC and store the input datareceived from the external device through NFC into the memory device1300. The NFC device 1200 may include a resonance unit 1210 and an NFCchip 1220. The resonance unit 1210 may provide data communication withthe external device through an electromagnetic wave. The NFC chip 1220may provide the output data to the resonance unit 1210, receive theinput data from the resonance unit 1210, reduce a Q factor (qualityfactor) of the resonance unit 1210 when a signal receive operation isperformed in a card mode, and maintain the Q factor of the resonanceunit 1210 in a reader mode and when a signal transmit operation isperformed in the card mode. The NFC device 1200 may be embodied with theNFC device 10 of FIG. 1. A structure and an operation of the NFC device10 are described with reference to FIGS. 1 to 24. [0250] The userinterface 1400 may include at least one input device, such as a keypad,a touch screen, etc., and at least one output device, such as a speaker,a display device, etc. The power supply 1500 may supply a power supplyvoltage to the electronic system 1000.

In some embodiments, the electronic system 1000 may further include animage processor, and/or a storage device, such as a memory card, a solidstate drive (SSD), a hard disk drive (HDD), a CD-ROM, etc.

In some embodiments, the electronic system 1000 and/or components of theelectronic system 1000 may be packaged in various forms, such as packageon package (PoP), ball grid arrays (BGAs), chip scale packages (CSPs),plastic leaded chip carrier (PLCC), plastic dual in-line package (PDIP),die in waffle pack, die in wafer form, chip on board (COB), ceramic dualin-line package (CERDIP), plastic metric quad flat pack (MQFP), thinquad flat pack (TQFP), small outline IC (SOIC), shrink small outlinepackage (SSOP), thin small outline package (TSOP), system in package(SIP), multi chip package (MCP), wafer-level fabricated package (WFP),or wafer-level processed stack package (WSP).

The foregoing is illustrative of the present inventive concept and isnot to be construed as limiting thereof. Although a few exampleembodiments have been described, those skilled in the art will readilyappreciate that many modifications are possible in the exampleembodiments without materially departing from the novel teachings andadvantages of the present inventive concept. Accordingly, all suchmodifications are intended to be included within the scope of thepresent inventive concept as defined in the claims. Therefore, it is tobe understood that the foregoing is illustrative of various exampleembodiments and is not to be construed as limited to the specificexample embodiments disclosed, and that modifications to the disclosedexample embodiments, as well as other example embodiments, are intendedto be included within the scope of the appended claims.

What is claimed is:
 1. An NFC (near field communication) device comprising: a resonance unit configured to make data communication with an external device through an electromagnetic wave; and an NFC chip configured to provide output data to the resonance unit, to receive input data from the resonance unit, to reduce a Q factor (quality factor) of the resonance unit when a signal receive operation is performed in a card mode, and to maintain the Q factor of the resonance unit in a reader mode and when a signal transmit operation is performed in the card mode.
 2. The NFC device of claim 1, wherein the NFC chip connects a terminal connected to the resonance unit to a ground voltage through a pull-down load when the signal receive operation is performed in the card mode and cuts off the terminal connected to the resonance unit from the ground voltage in the reader mode and when the signal transmit operation is performed in the card mode.
 3. The NFC device of claim 1, wherein the NFC chip measures a voltage supplied from the resonance unit and controls a reduction degree of the Q factor of the resonance unit based on a magnitude of the measured voltage when the signal receive operation is performed in the card mode.
 4. An NFC (near field communication) device comprising: a resonance unit configured to generate a first voltage in response to an electromagnetic wave; a rectifier configured to generate a second voltage by rectifying the first voltage; a regulator configured to generate an internal voltage having a voltage level of a constant magnitude by using the second voltage to output the internal voltage to a first node; and a Q (quality) sink unit connected between the first node and a ground voltage, the Q sink unit being turned on to reduce a Q factor (quality factor) of the resonance unit when a signal receive operation is performed in a card mode, and being turned off to maintain the Q factor in a reader mode and when a signal transmit operation is performed in the card mode.
 5. The NFC device of claim 4, wherein the Q sink unit comprises: a Q sink controller configured to generate a Q sink signal enabled when the signal receive operation is performed in the card mode and disabled in the reader mode and when the signal transmit operation is performed in the card mode; and a pull-down unit configured to connect the first node to the ground voltage through a pull-down load when the Q sink signal is enabled and to cut off the first node from the ground voltage when the Q sink signal is disabled.
 6. The NFC device of claim 5, further comprising: a central processing unit (CPU) configured to generate a mode signal that represents the card mode or the reader mode and the signal receive operation or the signal transmit operation when the mode is the card mode, wherein the Q sink controller generates the Q sink signal based on the mode signal.
 7. The NFC device of claim 5, wherein the pull-down unit comprises: a switch connected to the first node and turned on in response to the Q sink signal; and a current source connected between the switch and the ground voltage to generate a current having a constant magnitude.
 8. The NFC device of claim 5, wherein the pull-down unit comprises: a slew control unit configured to generate first to n^(th) Q sink sub-signals, which are sequentially enabled at a first time interval, when the Q sink signal is enabled and to generate first to n^(th) Q sink sub-signals, which are sequentially disabled at the first time interval, when the Q sink signal is disabled; first to n^(th) switches connected to the first node and turned on in response to the first to n^(th) Q sink sub-signals, respectively; and first to n^(th) current sources connected between the first to n^(th) switches and the ground voltage, respectively, to generate a current having a constant magnitude.
 9. The NFC device of claim 5, wherein the pull-down unit comprises: a switch connected to the first node and turned on in response to the Q sink signal; and a resistor connected between the switch and the ground voltage.
 10. The NFC device of claim 5, wherein the pull-down unit comprises: a slew control unit configured to generate first to n^(th) Q sink sub-signals, which are sequentially enabled at a first time interval, when the Q sink signal is enabled and to generate first to n^(th) Q sink sub-signals, which are sequentially disabled at the first time interval, when the Q sink signal is disabled; first to n^(th) switches connected to the first node and turned on in response to the first to n^(th) Q sink sub-signals, respectively; and first to n^(th) resistors connected between the first to n^(th) switches and the ground voltage, respectively.
 11. The NFC device of claim 4, further comprising: a field detector configured to receive the first voltage to generate a field intensity signal corresponding to a magnitude of the first voltage, wherein the Q sink unit controls a reduction degree of the Q factor of the resonance unit based on the field intensity signal when the signal receive operation is performed in the card mode.
 12. The NFC device of claim 11, wherein the Q sink unit comprises: a Q sink controller configured to generate a Q sink signal enabled when the signal receive operation is performed in the card mode and disabled in the reader mode and when the signal transmit operation is performed in the card mode and to generate a Q factor tuning signal based on the field intensity signal; and a pull-down unit configured to connect the first node to the ground voltage through a pull-down load having a magnitude corresponding to the Q factor tuning signal when the Q sink signal is enabled and to cut off the first node from the ground voltage when the Q sink signal is disabled.
 13. The NFC device of claim 12, wherein the pull-down unit comprises: a switch connected to the first node and turned on in response to the Q sink signal; and a variable current source connected between the switch and the ground voltage to generate a current having a magnitude corresponding to the Q factor tuning signal.
 14. The NFC device of claim 12, wherein the pull-down unit comprises: a slew control unit configured to generate first to n^(th) Q sink sub-signals, which are sequentially enabled at a first time interval, when the Q sink signal is enabled and to generate first to n^(th) Q sink sub-signals, which are sequentially disabled at the first time interval, when the Q sink signal is disabled; first to n^(th) switches connected to the first node and turned on in response to the first to n^(th) Q sink sub-signals, respectively; and first to n^(th) variable current sources connected between the first to n^(th) switches and the ground voltage, respectively, to generate a current having a magnitude corresponding to the Q factor tuning signal.
 15. The NFC device of claim 12, wherein the pull-down unit comprises: a switch connected to the first node and turned on in response to the Q sink signal; and a variable resistor connected between the switch and the ground voltage and having a resistance with a magnitude corresponding to the Q factor tuning signal.
 16. The NFC device of claim 12, wherein the pull-down unit comprises: a slew control unit configured to generate first to n^(th) Q sink sub-signals, which are sequentially enabled at a first time interval, when the Q sink signal is enabled and to generate first to n^(th) Q sink sub-signals, which are sequentially disabled at the first time interval, when the Q sink signal is disabled; first to n^(th) switches connected to the first node and turned on in response to the first to n^(th) Q sink sub-signals, respectively; and first to n^(th) variable resistors connected between the first to n^(th) switches and the ground voltage, respectively, and having a resistance with a magnitude corresponding to the Q factor tuning signal.
 17. An NFC (near field communication) device comprising: a resonance unit configured to generate an electromagnetic wave corresponding to a transmit signal received from a transmit terminal in a reader mode; and a transmit unit configured to generate the transmit signal corresponding to output data to provide the transmit data to the transmit terminal in the reader mode, to reduce a Q factor (quality factor) of the resonance unit when a signal receive operation is performed in a card mode, and to maintain the Q factor when a signal transmit operation is performed in the card mode.
 18. The NFC device of claim 17, wherein the transmit unit connects the transmit terminal to a supply voltage through a pull-up load or connects the transmit terminal to a ground voltage through a pull-down load based on the output data in the reader mode, connects the transmit terminal to the ground voltage through the pull-down load when the signal receive operation is performed in the card mode, and cuts off the transmit terminal from the ground voltage and the supply voltage when the signal transmit operation is performed in the card mode.
 19. The NFC device of claim 17, wherein the transmit unit comprises: a pull-up transistor connected between the supply voltage and the transmit terminal; a pull-down transistor connected between the ground voltage and the transmit terminal; and a driving unit configured to selectively turn on one of the pull-up transistor and the pull-down transistor based on the output data in the reader mode, to turn off the pull-up transistor while turning on the pull-down transistor when the signal receive operation is performed in the card mode, and to turn off the pull-up transistor and the pull-down transistor when the signal transmit operation is performed in the card mode.
 20. The NFC device of claim 19, further comprising: a central processing unit (CPU) configured to generate a mode signal that represents the card mode or the reader mode and the signal receive operation or the signal transmit operation when the mode is the card mode, wherein the driving unit drives the pull-yup transistor and the pull-down transistor based on the mode signal.
 21. The NFC device of claim 17, wherein the transmit unit comprises: first to n^(th) pull-up transistors connected in parallel between the supply voltage and the transmit terminal; first to n^(th) pull-down transistors connected in parallel between the ground voltage and the transmit terminal; and a driving unit configured to turn on the first to n^(th) pull-up transistors or the first to n^(th) pull-down transistors based on the output data in the reader mode, to turn off the first to n^(th) pull-up transistors while sequentially turning on the first to n^(th) pull-down transistors at a first time interval when the signal receive operation is performed in the card mode, and to turn off the first to n^(th) pull-up transistors while sequentially turning off the first to n^(th) pull-down transistors at the first time interval when the signal transmit operation is performed in the card mode.
 22. The NFC device of claim 17, further comprising: a field detector configured to measure a voltage supplied from the resonance unit to generate a field intensity signal corresponding to a magnitude of the measured voltage in the card mode, wherein the transmit unit controls a reduction degree of the Q factor of the resonance unit based on the field intensity signal when the signal receive operation is performed in the card mode.
 23. The NFC device of claim 22, wherein the transmit unit comprises: first to n^(th) pull-up transistors connected in parallel between the supply voltage and the transmit terminal; first to n^(th) pull-down transistors connected in parallel between the ground voltage and the transmit terminal; and a driving unit configured to turn on the first to n^(th) pull-up transistors or the first to n^(th) pull-down transistors based on the output data in the reader mode, to select k pull-down transistors (k is a positive integer equal to or less than n) among the first to n^(th) pull-down transistors based on the field intensity signal in the card mode, to turn off the first to n^(th) pull-up transistors and (n−k) pull-down transistors, which are not selected, while sequentially turning on the k pull-down transistors at a first time interval when the signal receive operation is performed in the card mode, and to turn off the first to n^(th) pull-up transistors and (n−k) pull-down transistors, which are not selected, while sequentially turning off the k pull-down transistors at the first time interval when the signal transmit operation is performed in the card mode.
 24. An electronic system comprising: an NFC (near field communication) device configured to make communication with an external device through an NFC: a memory device configured to store output data and input data; and an application processor configured to control operations of the NFC device and the memory device, wherein the NFC device comprises: a resonance unit configured to transmit the output data to the external device through an electromagnetic wave; and an NFC chip configured to provide the output data to the resonance unit, to receive the input data from the resonance unit, to reduce a Q factor (quality factor) of the resonance unit when a signal receive operation is performed in a card mode, and to maintain the Q factor of the resonance unit in a reader mode and when a signal transmit operation is performed in the card mode.
 25. A method of operating a Near Field Communication (NFC) device, the method comprising: operating a resonance circuit with a first quality factor responsive to at least a first operation of the NFC device; and operating the resonance circuit with a second quality factor, that is less than the first quality factor, responsive to at least a second operation of the NFC device that is different than the first operation of the NFC device.
 26. The method of claim 25 wherein operating the resonance circuit with a second quality factor comprises reducing a gain of the resonance circuit from a first gain value to a second gain value.
 27. The method of claim 26 wherein the first and second gain values comprise first and second voltage gain values, respectively.
 28. The method of claim 26 wherein the first gain value of the resonance circuit is associated with the first operation of the NFC device and the second gain value of the resonance circuit is associated with the second operation of the NFC device.
 29. The method of claim 26 wherein the first gain value is defined as a maximum value for a response of the resonance unit as a function of frequency over a first bandwidth and the second gain value is defined as a maximum value for a response of the resonance unit as a function of frequency over a second bandwidth; wherein reducing a gain of the resonance circuit from a first gain value to a second gain value further comprises: increasing the bandwidth of the resonance unit from the first bandwidth to the second bandwidth.
 30. The method of claim 25 wherein the first operation of the NFC device comprises at least one of an operation in a reader mode for the NFC device and a signal transmit operation in a card mode for the NFC device.
 31. The method of claim 25 wherein the second operation of the NFC device comprises a signal receive operation in a card mode for the NFC device.
 32. The method of claim 29 wherein operating the resonance circuit with a second quality factor comprises electrically coupling a terminal of the resonance circuit to a ground voltage through a pull-down circuit in the second operation of the NFC device.
 33. The method of claim 30 wherein operating the resonance circuit with a second quality factor comprises electrically decoupling a terminal of the resonance circuit from a ground voltage in the first operation of the NFC device.
 34. The method of claim 25 wherein operating the resonance circuit with a second quality factor comprises: determining a magnitude of a voltage signal provided by the resonance circuit; providing a signal indicating an amount of reduction to the quality factor based on the magnitude of the voltage signal to provide the second quality factor; and operating the resonance circuit with the second quality factor second responsive to the second operation of the NFC device. 